Recommended Compression Tester?

[bowhunter11199]

While looking to buy a sled, I would like to be able to test the cylinder compression. I understand my tester may not be very accurate because I don’t want to pay for a MATCO or snap on. My main concern is if the gauge is repeatable so I can see how close the cylinders are to each other


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[bowhunter11199]

Bump


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[05rmksteve]

I've had good and bad results with compression testers. Had someone that wanted to buy a sled from me and he brought his own new mac tester. When using his tester on cylinder was at 64 the othe was 58. I hooked up my inexpensive tester and had 124 and 122. I've also used a snap on tester that would read 20 psi higher than other testers. I've had better luck with the mid rang testers. But the best way to tell the condition of the top end is to do a top end leak down test.

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[Big10inch]

Agreed on the leak down test. The compression test is not reliable and wont really tell you the condition of the pistons, rings and cylinders like the leak down will. Way too many instances where compression read good but leakdown and run quality were bad.

 

[bowhunter11199]

Agreed on the leak down test. The compression test is not reliable and wont really tell you the condition of the pistons, rings and cylinders like the leak down will. Way too many instances where compression read good but leakdown and run quality were bad.

Steve and Big 10,

In your experience how many sled owners let you do a leak down test on their sled when you were looking at buying it?


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[05rmksteve]

The last dozen or so sleds that I've bought have either been brand new or have had bad motors. But if some one wants to do a top end leak down test on a sled they're buying from me their more than welcome I'll even let them use my tester or I'll do the test for them.

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[05rmksteve]

But most people dont have a clue on how to do a top end leak down test or what it even is. Its always a compression test. I have not once yet been asked for the leak down #'s. or to do a leak down test on a sled that in selling.

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[bowhunter11199]

So what I’m hearing is that a compression test is essentially worthless and shouldn’t be done??

It seems to me that it’s at least worth doing, but I was unsure if I should buy a cheap harbor freight or a somewhat nicer one


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[05rmksteve]

A compression test can tell you if the compression is low or if 1 side has low compression and the other side is ok.

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[Big10inch]

I have sold 4 used sleds in the last year or so, never been asked for a leak down or compression test but these were all Cat's with ~2000 miles, and typically they run double that without issues. If you are looking at Polaris I would insist on a leakdown regardless of miles as I believe many of those leave the factory with poor cylinder finish.

The inexpensive leak down testers seem as accurate as the expensive ones. Buy one instead of the compression tester. The only flaw in remote testing is the need for a decent air compressor.